Helpers are needed to prepare for the fete. Each helper can make either 2 large cakes per hour, or 35 small cakes per hour. The kitchen is available for 3 hours and 20 large cakes and 700 small cakes are needed. How many helpers are required?
(A) 10
(B) 15
(C) 20
(D) 25
(E) 30

Source: majortests.com

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